There are a number of candidates for the 6.5-7.5cc DF engine crowd, as well as for hot .15-.21 engines.

I have some 4.25 props in 4.5 - 5.5 pitch to try out on the Profi. I bought a couple of the .010 props but they are tough to balance well with the wee hole. Nice idea, but the Cox black props are easy to get these days.

MJD